Problem: Simplify the following expression: $y = \dfrac{1}{4z} + \dfrac{1}{2z}$
Explanation: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $4z$ and $2z$ $\lcm(4z, 2z) = 4z$ $ y = \dfrac{1}{1} \cdot \dfrac{1}{4z} + \dfrac{2}{2} \cdot \dfrac{1}{2z} $ $y = \dfrac{1}{4z} + \dfrac{2}{4z}$ $y = \dfrac{1 +2}{4z}$ $y = \dfrac{3}{4z}$